Tube Filter Housing / Candle Filter

Primary Purpose

The core function of a tube filter housing is to efficiently and precisely separate and capture solid particles from industrial liquids. Key objectives include:

Clarification: Removing fine suspended solids to improve product clarity.

Valuable Solids Recovery: Recovering materials like catalysts, activated carbon, or precious metal powders.

Process Liquid Purification: Protecting downstream equipment (e.g., reactors, crystallizers, fillers) by ensuring feed liquid cleanliness.

Waste Treatment & Environmental Protection: Performing solid-liquid separation for wastewater prior to discharge or reuse.

Working Principle

It operates on a combination of "cross-flow/surface filtration" and a precoat technique. The process is cyclical:

Stage 1: Precoating & Circulation

A uniform, stable precoat layer (2-5 mm thick) is formed on the bare filter elements (candle tubes) by circulating a slurry of filter aid (e.g., diatomaceous earth, perlite, activated carbon).

This precoat layer acts as the primary filtering medium, determining the final filtration grade.

Stage 2: Filtration

The process liquid is pumped into the pressure vessel, flowing perpendicularly (cross-flow) across the surface of the precoated candles.

Solids are trapped on the surface of the precoat, while the clean filtrate passes through the precoat layer and the tube's micro-porous structure, collecting inside the candle and exiting via the clean outlet.

As filtration continues, the captured solids build up, forming a filter cake, which further aids filtration but gradually increases pressure drop.

Stage 3: Cake Discharge (Blow-down / Cleaning)

When the differential pressure reaches a set limit or the batch is complete, filtration stops.

The key step: Reverse Air/Blow-back. Compressed air or gas is introduced in reverse flow—from inside the candles outward. This rapidly expands the tubes, cracking and dislodging the entire cake layer.

The discharged (often dry) cake falls by gravity to the conical bottom sludge hopper and is evacuated through a discharge valve.

Stage 4: Cleaning & Standby

Elements can be rinsed or cleaned chemically if needed, preparing the system for the next cycle.

Key Advantages

Compared to traditional filter presses or bag filters, tube filter housings offer significant benefits:

High Filtration Efficiency & Clarity: Achieves high precision (down to 0.1 µm) by selecting appropriate filter aids.

Handles Challenging Slurries: Excellent for viscous, gelatinous, or fine, compressible solids that would blind other filters.

Fully Closed, Hygienic System: Operates leak-free, preventing vapor release and contamination. Ideal for CIP/SIP (Clean-in-Place/Sterilize-in-Place) processes in food, pharmaceutical, and solvent applications.

Dry Cake Discharge: The reverse blow-back enables dry cake discharge with high solid content (30%-70%), reducing drying costs and aiding solids recovery.

High Automation: Easily integrated with PLC for full automation of all cycles, reducing labor and ensuring consistency.

Low Operational Cost: Rigid candle elements are durable and reusable. Filter aid is the primary consumable, often more economical than disposable filter cloths or bags.

Compact Footprint: Integrated design requires less floor space.

 Major Application Fields

Widely used in industries requiring high purity, hygiene, and automation:

Chemicals & Petrochemicals: Catalyst recovery, polymer separation, solvent polishing, lube oil filtration.

Food & Beverage: Clarification of beer, wine, juices, edible oils, syrups, and condiments.

Pharmaceutical & Biotechnology: Harvesting of active pharmaceutical ingredients (APIs), fermentation broth clarification, cell debris removal, sterile filtration of parenterals.

Coatings, Paints & Inks: Removal of gels and impurities from resins and pigments to enhance gloss and stability.

Environmental & Water Treatment: Polishing of industrial wastewater, dewatering of metal hydroxide sludges, process water fine filtration.

Others: Nanomaterial slurry filtration, metalworking fluid cleaning, electroplating bath treatment.